Quick quantification of proteins by MALDI

Area of Science:

• Analytical Chemistry
• Biochemistry
• Mass Spectrometry

Background:

• Reproducible peptide quantification via matrix-assisted laser desorption ionization (MALDI) requires controlled conditions.
• Previous work established peptide quantification using a calibration curve without internal standards.

Purpose of the Study:

• To quantify proteins by quantifying their tryptic peptides using an established MALDI method.
• To adapt and simplify the sample preparation for direct protein quantification.

Main Methods:

• Proteins were digested, with disulfide bonds intentionally not cleaved, minimizing residual reagents.
• Sample preparation involved direct mixing of the digestion mixture with a matrix solution.
• Quantification was achieved by measuring the peptide-to-matrix ion abundance ratio.

Main Results:

• Protein quantification was successfully performed by quantifying tryptic peptides.
• A simplified sample preparation allowed direct mixing of digestion mixture and matrix.
• The method demonstrated rapid protein quantification using an averaged reaction quotient for peptides with C-terminal arginine.

Conclusions:

• This method enables protein quantification without the need for peptide standards or isotopically labeled analogs.
• The simplified protocol enhances the efficiency of MALDI-based protein analysis.
• The findings offer a robust approach for reproducible and accurate protein quantification.